﻿Shader "PostEffect/SceneFadeEffect"
{
	Properties
	{
		_MainTex ("Texture", 2D) = "white" {}
		_Angle("Angle", Float) = 0.0
		_MaskColor("MaskColor", Color) = (1,1,1,1)
		_IsForward("IsForward", Int) = 0
	}
	SubShader
	{
		// No culling or depth
		Cull Off ZWrite Off ZTest Always

		Pass
		{
			CGPROGRAM
			#pragma vertex vert
			#pragma fragment frag

			#include "UnityCG.cginc"

			struct appdata
			{
				float4 vertex : POSITION;
				float2 uv : TEXCOORD0;
			};

			struct v2f
			{
				float2 uv : TEXCOORD0;
				float4 vertex : SV_POSITION;
			};

			v2f vert (appdata v)
			{
				v2f o;
				o.vertex = UnityObjectToClipPos(v.vertex);
				o.uv = v.uv;
				return o;
			}

			sampler2D _MainTex;
			float _Angle;
			fixed4 _MaskColor;
			int _IsForward;

			fixed4 frag (v2f i) : SV_Target
			{
				fixed4 col = tex2D(_MainTex, i.uv);
				float2 dir = i.uv - float2(0.5, -0.005f);

				//做个模糊反走样
				float threshold = 0.001f;	//模糊边界的阈值(单位为弧长)
				float dis = -sin(_Angle) * dir.x + cos(_Angle) * dir.y;
				float r = 0.5 * (dis - threshold) / threshold;
				r = max(r, 0); r = min(r, 1);   //r代表输出颜色中白色占的比例

				//当IsForward=0，对r反向; 反之r不变
				r = _IsForward * r + !_IsForward * !r;

				//输出颜色
				col = 1 - r * (1 - col);

				return col;
			}

			ENDCG
		}
	}
}
